This invention relates to a small portable machine for testing adhesion coatings to various substrates such as pipes or the like.
Good adhesion is essential for good performance of a coating in most industrial applications, with one exception being strippable coatings. A good coating system involves:
1. Selecting a coating with properties permitting it to adhere to the substrate's surface.
2. Preparing the substrate surface properly.
3. Applying the coating so it will achieve good adhesion.
If adhesion performance of a coating material is not known, some means must be available to determine the degree of adhesion and to relate it to some base value. Unfortunately, there are no commonly accepted absolute criteria of adhesion values expressible in concrete terms. Many adhesion tests involve subjective judgments. Even numbers obtained from machine performed tests are not clearly defined.
There are many laboratory type machines presently available for testing adhesion of a protective coating on a specially-prepared panel. The panels are ordinarily prepared in a laboratory under ideal conditions.
U.S. Pat. No. 2,533,076 issued to D. M. Williams on Dec. 5, 1950 and is directed to an apparatus for testing the adhesion of films of coating material. The Williams apparatus is not of the portable type and is designed to test the adhesion characteristics of flat surface films. U.S. Pat. No. 2,530,257 issued to J. R. Marcus on Nov. 14, 1950 and discloses an apparatus for testing coatings applied to a flat surface. More particularly, the Marcus device is designed to test the mar resistance and scratch adhesion of paints and is not portable. U.S. Pat. No. 3,124,955 issued to G. E. Naslund on Mar. 17, 1964 and involves a pendulum type apparatus designed to determine the adherence of a coating bonded to a surface. In Naslund, an elongated strip of tape must be adhered to the flat test surface so that the swinging pendulum will strike the tape and the amount of force required to separate the tape from the surface is recorded by an indicator arm. U.S. Pat. No. 2,498,265 issued to H. Green on Feb. 21, 1970 and relates to a non-portable apparatus for testing the adherence of coating films on a flat surface.
Coatings, especially pipe-line coatings, applied in the field are not applied under ideal conditions; and, therefore, do not always perform as expected. Adhesion may deteriorate with time due to temperature variations, soil stresses, ground water and natural aging of the coating. Currently, the available testing machines cannot be used for testing in-place coatings. A common procedure for testing in-place coatings in the pipe-line industry is to scribe an "x" through the coating into the substrate with a sharp knife. Then, holding the knife at a 35.degree. to 40.degree. angle, the blade point is inserted at an intersection of the scribe and pushed into the coating firmly and constantly while making mental notes of the force required, flaking caused, and degree of adhesion of the coating. The degree of adhesion is then rated against a similar test performed on an unexposed or control panel.
Therefore, it is a principal object of the invention to provide a small portable machine for testing adhesion of coatings to various substrates.
A further object of the invention is to provide a small portable machine which may be used for testing adhesions of coatings while the coating is in place.
A still further object of the invention is to provide a machine for testing adhesion of coatings which allows evaluation of the coating system after the coating system has been applied in the field under conditions which may be far from ideal.
A still further object of the invention is to provide a machine for testing adhesion of coatings which does not require special operator training.
A still further object of the invention is to provide a machine for testing adhesion of coatings including means for visually indicating the force required to sever the coating from the substrate.
A still further object of the invention is to provide a machine for testing adhesion of coatings including means for varying the amount of weight applied to the knife blade associated therewith.
A still further object of the invention is to provide a machine for testing adhesion of coatings to various substrates which is economical to manufacture, durable in use and refined in appearance.
These and other objects will be apparent to those skilled in the art.